Hot workable nickel alloy



Patented May 20, 1952 HOT WORKABLE NICKEL ALLOY John Harry Jackson and rien W. Simmons,

Columbus, Ohio, assignors, by mesne assignments, to The Illium Corporation, Freeport,,Ill., a corporation of Delaware I No Drawing. Application August 3,

Serial N0; 177,556

Claims.

This invention relates to corrosion resistant alloysand particularly to alloys characterized by their unusual high resistance to corrosion, the ease with which they can be hot-worked, and their resistance to scale formation during hot working. More particularly, the invention relates to improvements in nickel-chromium alloys.

A previously known alloy of this type was de- .Veloped by the late Professor S. W. Parr of the University of Illinois and is described in United States Patent 1,115,239, dated October 27, 1914 and was reported by Professor Parr in the Transactions of the American Institute of Metals, volume 9, pages 2112l7, 1915. This original alloy was developed of base metals primarily for use incalorimete'r bombs. It has been known and widely used since its development, its utility having resulted from its economical base metal composition coupled with its resistance to corrosion, density, strength when subjected to high pressure, and also its machinability. Its use has been almost entirely confined to the making of castings because it possessed only limited hotworkability. Since the development of the original alloy, the composition has been modilied and the recent composition prior to the present invention is substantially as follows: chromium 22.5%, molybdenum 6.4%, iron 6.5%, copper 6.5%, manganese 1.25%, silicon 0.65%, carbon 0.20%, balance nickel (56.0%). All compositions given herein are on a weight basis. I

The said known nickel-chromium alloy, while of great utility because of its extraordinary resistance to oxidizing and non-oxidizing acids, has

been essentially limited as stated heretoforeto e the making of castings because it does not possess the hot-ductility required for hot working operations such as forging, rolling, drawing, etc. For example, in hot rolling such alloy, special equipment and laborious technique have been required. Also, the range of ductility has been small and the alloy isnot workable except in this narrow range. As a result, the alloy was not forged or otherwise hot-worked to any substantial extent and ingots large enough to be con-- 1 sidered of commercial size were never successfully hot-worked.

In contrast, the alloy of the present invention, in addition to possessing superior corrosion resisting properties, is capable of being readily forged, rolled, drawn, etc. utilizing standard commercial machinery such as is at present used in For. vexam ne, whereas the prior alloy when hot" rolled gouldnot successfully be reduced in thickthe-production of steel and stainless steel.

ness at a rate ofmore than 1% per pass, the present alloy' can be reduced at the rate of 10% to 20% per pass in commercial machinery. "In experimental tests, reductions in thickness as great as 65% have been accomplished. Also, this hot-ductility exists in a 400 degree F. temperature range from1950 F. to 2350 F. without brittleness, while with. the prior alloy the ductility range was only about 100 degrees F., usually from 2000 F. to 2100 F. In addition, the actual hot ductility of the alloy is greater than that of the prior alloy. .In addition, the alloy possesses a high degree of resistance to oxidation and there is a remarkable freedom from scale formation at temperatures from room'temperature (70 F.) to 2350 F. Also, it possesses great strength at temperatures up to 1900- F. Actual tests will be described hereinafter demonstrating the superior corrosion resistance-and'hotworkability of the'alloy of the invention.

It is, therefore, the object of the invention to provide an alloy of, the character described which possesses superior corrosion resistance and hot-workability and also the other desirable properties described heretofore.

In accordance with the present invention, the

composition of the improved alloy is as follows:

chromium 17% to 24%, molybdenum'3% to 5%,

1 copper 1.5% to 4%., iron less than 10%, carbon .02% to .15%, manganese and silicon not more than the maximum amounts described hereinafter andthe balance nickel. For best results, the maximum amounts of all of the elements other than nickel as given in the foregoing ranges may not be present in the alloy. Best results are obtained when the maximum amounts given in said ranges are used with the following limitations. 'If the amount of chromium does not exceed 18%, all of the elements, other than,

nickel and chromium, may be at the maximum amounts; if the amount of carbon does not exceed. .05 all of the elements, other than carbon and nickel may be at the maximum amounts. With the exception of thesetwo conditions, all of the elements, other than nickel, may be at the maximum amounts given in the foregoing ranges, and all of the elements, other than nickel, may be at the minimum amounts in said ranges, and an alloy will in each case result which has excellent corrosion resistance, hot

I workability, and resistanceto scale formation while being hot worked. i; The preferred composition for the alloy of the 1 present invention is asfollows: chromium'.20%

to 23%, molybdenum 4%;to 5%,copper. 2%

to 3%, iron 5% to 7%, carbon .03% to .08%, manganese and silicon not more than the maximum amounts described hereinafter, the balance being nickel. Any combination of elements within the ranges set forth in the foregoing preferred composition may be used and will result in an alloy having superior resistance to corrosion, hot workability, and resistance to scale formation while being worked.

A suitable method for forming. the alloy is as follows: The chromium, iron, carbon, nickel and copper are charged into a furnace andheating. of the furnace is commenced. Melting of the metal is carried out under oxidizing conditions. The use of a nickelous oxide slag produces very satisfactory results. After a substantial bath of molten metal has been formed, the molybdenum is added and heating is continued until the metal is molten and the temperature has reached about 2850 F. to 2900 F. Any slag present on the molten bath is removed. After this operation, suificient manganese. and silicon are added to effect desulfurization and deoxidation while. holding the residual amounts of. these metals at a mminimum. A slag is then added which serves as a protective cover for the molten metal. A suitable slag for this purpose is one-composed of lime, alumina and magnesia, and it is maintained in reducing condition by small additions of aluminum. Final traces of oxygen, nitrogen and present invention, the following test results are given Test 1.

A previously known alloy having the analysis chromium 22%, molybdenum 6.5%, iron 6.7%,

copper 6.2%, manganese 1.2%, silicon 55%, carbon 23%, and the balance nickel was immersed in a boiling aqueous nitric acid solution, containing 65% by weight of HNO3. During immersion the specimen was supported on three pointed supporting members of glass. Immersion was continued for 48 hours. The specimen was then removed. from the acidbath, rinsed with distilled water and then. with ethyl alcohol. It was then dried and weighed. The loss in weight was computed in terms of the reduction in thickness which a large plate of the alloy would undergo under similar corrosion conditions in a period of one year, which is a commonly used method of presenting corrosion data. For the alloy in question, the average corrosion of several specimens was equivalent. to a .reduction in thickness of 0.37550 inch per year.

Test 2 4 Test 3 An alloy having the same composition as that used in Test 1 was immersed in an aqueous solution of sulfuric acid, containing 10% by weight of H2504. for 48 hours, the procedure of the test being the same as that described in connection with Test 1. The average corrosion was equivalent to a reduction in thickness of .01133 inch per year.

Test 4 An alloy similar to that described in connection with Test 2 was immersed in an aqueous sulfuric acid solution containing 10% by weight of H2804 for 48 hours, the test procedure being the same as in Test 1. The average corrosion was equivalent to a reduction in thickness of .01000 inch per year.

The above tests show the superior corrosion resistance of the alloy of the present invention. With respect to hot workability, ingots of the alloy of the present invention after being forged into a rod- 2- inches square in cross section have been successfully rolled into the form of a cylindrical rod inch in diameter on a highspeed continuous rod mill such as is used in the commercial rolling of steel, in which a reduction in transverse dimensions of approximately 20% was accomplished at each pass. The total reduction was accomplished with one heating, that is, without any reheating between passes. Rolling such as this was impossible with the previously known type of alloy, in which a reduction of 1.0% in transverse dimension was the most which could be accomplished at one pass and required special machinery and frequent reheating. Furthermore, with the present alloy such rolling has been successfully accomplished at various temperatures from 1950" F. to 2350 F., showing that it can be done at any temperature in this range. With the former alloy the rolling could be accomplished only in the range 2000 F. to 2100 F.

As further evidence of hot workability, the present and former alloys were subjected tohot compression and hot bending tests. In the hot compression test, a one inch cube of the metal was held in the furnace at the desired temperature for one half hour and then compressed the desired controlled amount quickly so that there was no loss in temperature during the operation. Such tests have been carried out using either a single blow of a forging hammer or the pressure of a quick acting hydraulic press. The alloy of the present invention was successfully compressed to one third its original thickness at temperatures from 2000 F. to 2300 F., the sides bulging without exhibiting any cracking. In contrast to this the former alloy withstood compression to 57% of its original thickness at only 1800" F. to 1900 F. and at temperatures outside this'range or at higher degrees of compression it exhibited severe cracking.

For the hot-bending test, a specimen x 1" at 3 /3" was'flrstprepared by forging and cutting and given an initial bend of 20 degrees at its mid-point while cold. It was then placed in the furnace and held at the desired hot-bending temperature for one half hour and then quickly pressed by a hydraulic press into the form of a U and the sides of the U pressed together. If the specimen underwent this bending without developing any surface cracks, it was considered to be, satisfactory. The alloy of the present invention consistently tested satisfactory at temperaures: from 2000 F. 1202300 F. Theformer-alIoy could not be consistently bent as described at temperatures from 1600 F. to 2400 F. In the narrow range of 2000 F. to 2100 F. a few specimens were successfully bent, but only a small proportion of the number of specimens tested in this range.

In the rolling, compression and bending tests described in the foregoing, the composition of the alloy of the present invention which was tested was nickel 64%, chromium 22%, molybdenum 5%, iron 6%, copper 2.5%, manganese .35%, silicon .15%, carbon .05%. The composition of the previously known alloy which was tested was nickel 57.9%, chromium -23.6%, molybdenum 6.4%, iron 6.5%, copper 4%, manganese 1.75%, silicon 35% and carbon .10%.

The foregoing information shows that the alloy of the present invention possesses superior ductility when hot and that it possesses ductility over a relatively wide temperature range. It exhibits the additional advantage mentioned heretofore that it is remarkably free from scale formation during hot working, and in this respect is superior to the previously known alloy.

What is claimed is:

1. A corrosion-resistant, hot-workable alloy comprising essentially by weight chromium 17% to 24%, molybdenum 3% to 5%, iron less than copper 1.5% to 4%, carbon .02% to .15%, and the balance nickel.

2. A corrosion-resistant hot-workable alloy comprising essentially by weight chromium 17% to 24%, molybdenum 3% to 5%, iron less than 10%, copper 1.5% to 4%, manganese less than 6 0.6%, silicon less than 0.4%, carbon .02% to .15%, and the balance nickel.

3. A corrosion-resistant, hot-workable alloy comprising essentially by weight chromium 20% to 23%, molybdenum 4% to 5%, iron 5% to 7%, copper 2% to 3%, carbon .03% to .08%, and the balance nickel.

4. A corrosion-resistant, hot-workable alloy comprising essentially by weight chromium 17% to 24%, molybdenum 3% to 5%. iron less than 10%, copper 1.5% to 4%, carbon .02% to .05%, and the balance nickel.

5. A corrosion-resistant, hot-workable alloy comprising essentially by weight chromium 17% to 18%, molybdenum 3% to 5%, iron less than 10%, copper 1.5% to 4%, carbon .02% to .15%, and the balance nickel.

JOHN HARRY JACKSON. ORIEN W. SIMMONS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,115,238 Parr Oct. 27, 1914 1,115,239 Parr Oct. 27, 1914 2,103,855 La Bour Dec. 28, 1937 2,293,878 Allen et al Aug. 25, 1942 OTHER REFERENCES Parr, Treatise in Trans. of The Amer. Inst. of Metals, vol. IX, 1915, pages 211-217. 

2. AN CORROSION-RESISTANT, HOT-WORKABLE ALLOY COMPRISING ESSENTIALLY BY WEIGHT CHROMIUM 17% TO 24%, MOLYBDENUM 3% TO 5%, FROM LESS THAN 10%, COPPER 1.5% TO 4%, MANGANESE LESS THAN 0.6%, SILICON LESS THAN 0.4%, CARBON .02% TO .15%, AND THE BALANCE NICKEL. 